Dance music is music composed specifically to facilitate or accompany dancing. It can be either a whole musical piece or part of a larger musical arrangement. In terms of performance, the major categories are live dance music and recorded dance music.
The origins of rock 'n' roll are as foggy as the genre is popular; the term was coined in 1955 by Alan Freed, a disc jockey from Ohio. The oldest form of rock 'n' roll (1950s) was a mixture of R&B, country and rockabilly (it was just called hillbilly music back then), only it was faster, louder and 'dangerous'.
Country music is music that developed from Southern American folk and western cowboy music in the rural regions of the Southern United States in the 1920s. Dance tunes and ballads with harmonies and simple form played with banjoes, acoustic and electric guitars, harmonicas and fiddles.